1. Field of the Invention
The present invention relates to an improvement in a light-emitting diode (LED), more specifically to an LED having high emission efficiency and an effective focusing property.
2. Description of Related Art
Conventionally known is a packaged LED including a blue LED element emitting blue light and a resin for sealing the blue LED element and containing therein a YAG fluorescent material which is excited by the emitted blue light and emits yellow light (for reference, see JP 2001-345482 A, FIGS. 1, 2 and 3, pages 3 and 4, and JP2002-94128 A, FIG. 1, page 3). In the LED, the blue light emitted from the blue LED element and the yellow light from the fluorescent material are mixed in the eye of the viewer to appear to the viewer as white light.
Also known is an LED lamp, including an LED element emitting near-ultraviolet light and an RGB fluorescent material, which is capable of emitting with a strong emission intensity almost the same white light as the white light for general lighting, having balanced color components of the primary colors red, green and blue through excitement of the RGB fluorescent material by the near-ultraviolet light from the LED element (for reference, see JP 2002-226846 A, FIG. 1, paragraphs 0016 to 0022).
Generally, in a surface-mounted LED, the LED element and wiring circuit are wire-bonded or flip-chip-connected in a reflecting cup.
However, when one portion of the blue light emitted from the blue LED element excites the YAG fluorescent material and the yellow light is emitted, because the whole of the resin containing the fluorescent material is lighted, the emission part or surface occupies an area larger than the size of the LED element. Therefore, if a lens is further combined with the LED element, because the light-emitting part is larger than the aperture of the lens, a sufficient collection property of the lens is not obtained. Moreover, because the resin containing the fluorescent material looks to be tinged yellow, if the LED is used for illumination, the quality of outward appearance of the lighting equipment is reduced by the tinge of yellow of the fluorescent material. Therefore, various makers have attempted to eliminate the tinge of yellow by placing a white diffuser in front of the LED.
However, there is a problem that disposing a white diffusion plate causes attenuation of emission output of the LED, or diffusion or attenuation of light collected by the lens.
In addition, if an LED element emitting near-ultraviolet light and an RGB fluorescent material are combined, the reduction in quality of outward appearance due to the tinge of yellow is less, but there is a problem that the collection property of the lens is insufficient if the area of the resin including the fluorescent material is large.